This application relates to a gas turbine engine having a gear reduction between a fan drive turbine and a fan and an electric auxiliary oil pump to supply oil during windmilling conditions.
Gas turbine engines are known and, typically, include a fan delivering air into a compressor. The air is compressed and delivered into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.
In one known type of gas turbine engine, a low pressure turbine drove both a low pressure compressor rotor and the fan rotor at a single speed. More recently, it has been proposed to provide a gear reduction such that the fan rotor can rotate at slower speeds than the low pressure compressor rotor.
The gear reduction requires lubrication, especially, at bearings. Thus, a pump is provided that adequately lubricates the bearings when the gas turbine engine is being driven.
However, gas turbine engines may sometimes be shut down when an associated aircraft is in the air. When this occurs, air is driven across the fan rotor and can cause the fan rotor to rotate. This is called “windmilling ” When windmilling occurs, the gear reduction is rotated and lubricant is required at the bearings and other surfaces.
Thus, it has been proposed to include an auxiliary oil pump, wherein an idler gear which rotates with a portion of the shaft, drives a mechanical gear driven oil pump. However, windmilling can occur in either direction of rotation and the proposed system only operates with one direction of windmilling rotation.